The Chinese leader knows that now.
Since the beginning of 2016, North Korea has carried out a number of missile launches and nuclear tests, prompting worldwide criticism.
Trump landed about an hour later and greeted Xi at Mar-a-Lago.
Trump, according to administration officials, informed President Xi during their meetings last week that if China was not successful in dissuading North Korea from further provocative actions, the United States is prepared to take action on its own.
Trump had said he meant to raise concerns about China's trade practices and press Xi to do more to rein in North Korea's missile and nuclear programs during their summit meeting at his Spanish-style Mar-a-Lago resort though no major deals on either issue were expected. He's also criticized China for grabbing jobs that could otherwise go to Americans.
Washington denies it has any intention of invading the North.
Trump met with China's president earlier this week in Florida.
In turn, an affable Trump was optimistic over the prospects of "a very, very great relationship" with China, describing his personal relationship with Xi as "outstanding".
The leaders of the world's two most powerful economies agreed to a 100-day plan to discuss trade talks directed at boosting U.S. exports and reducing Washington's trade deficit with China, according to Commerce Secretary Wilbur Ross.
The response by North Korea's Foreign Ministry, carried by the official KCNA news agency, was the first since USA warships in the Mediterranean Sea launched dozens of missiles at a Syrian air base which the Pentagon says was involved in a chemical weapons attack earlier in the week.
Stockholm truck attack suspect was failed asylum seeker, 2nd man arrested
He was given four weeks to leave the country in December but could not be located because he had given police a wrong address . Police Spokesman Lars Bystrom has since told news agencies , "We suspect that the man who was arrested is the perpetrator".
In a briefing on the outcome of the summit, Tillerson added that while the two leaders focused on both countries' commitments to denuclearize the Korean Peninsula, there "was no kind of a package arrangement discussed to resolve this".
But while the move might give the North pause, it is unlikely to deter a leadership that views nuclear weapons as the sole guarantee of its future survival.
"North Korea's posture has to change before there's any basis for dialogue or discussions", Tillerson said.
The United States is vowing to keep up the pressure on Syria after the intense nighttime wave of missile strikes from USA ships, despite the prospect of escalating Russian ill will that could further inflame one of the world's most vexing conflicts.
Trump informed the Chinese leader personally of the strike as the 59 Tomahawk missiles were winding their way to the Shayrat airbase.
The White House, in its statement released Sunday about the previous day's call, said Trump thanked Abe for his support of the US missile strikes and they "also agreed to further cooperation on a range of regional issues, including the threat posed by North Korea".
The New York Times reported last week that the Trump administration was looking to roll out its first measures against China on trade. "I don't think there's any appetite in the United States for a massive additional military presence, with young men and women actually in combat situations being introduced". It was the first direct USA assault on the Russian-backed government of Bashar al-Assad in six years of civil war.
"There is a real commitment to work together to see if this can not be resolved in a peaceful way", said Tillerson.
"If China shows an uncooperative attitude toward the North Korea nuclear issue", a government source in Seoul said, "Trump has made clear that he intends to actively implement secondary sanctions and is reviewing administrative procedures". Despite the use of chemical weapons in 2013, described as one of the worst chemical attacks in the last half century, the US and its main ally the United Kingdom chose not to conduct a military intervention, though they launched another one on Daesh, building an global coalition to do so. -China summit based on announced results.